1. Field of the Invention
The present invention relates to an adjusting drive for an adjustable part of a piece of furniture, particularly for adjusting the height and/or the lying surface of a bed such as, e.g., a hospital bed or nursing bed.
2. Description of the Prior Art
Electrically adjustable pieces of furniture such as, e.g., height-adjustable tables, armchairs and chairs with seat and/or backrest adjustment, or also beds, particularly hospital beds or nursing beds with height and/or lying-surface adjustment will require very compact adjusting drives which need merely low maintenance, are easy to install and are functionally reliable. Examples of such adjusting drives are found in DE 296 96 367 U1, DE 20 2007 006 469 U1, DE 20 2007 005 308 U1, EP 1 400 726 A1, EP 0 662 573 B1 and DE 103 29 097 A1.
These known adjusting drives comprise a housing and a gear transmission arranged within the housing. Normally, said gear transmission comprises a rotatable, motor-driven drive element and a driven element adapted to be brought into operative connection with the adjustable part of a piece of furniture. Said drive element is normally driven by an electric motor whose drive shaft has the drive element connected to it for common rotation therewith.
For automatic control of a piece of furniture provided with several adjusting drives, as is the case e.g. in a hospital bed or nursing bed with height adjustment and/or lying-surface adjustment, it is of advantage under the aspect of wiring minimization if the individual adjusting drives are connected to a bus which is controlled e.g. by a central control unit. In addition to the adjusting drives, however, such a piece of furniture advantageously comprises also position or displacement sensors for indicating the current adjustment position of an adjusted part of the piece of furniture.
Also these displacement sensors are normally connected to said bus. Each unit connected to the bus requires a bus communication interface with corresponding electronics, resulting in undesired technical expenditure and complicating the bus protocol and the bus communication.
In view of the above, it is an object of the invention to provide an adjusting drive for an adjustable part of a piece of furniture, wherein the feedback of the position of the part to be adjusted by the adjusting drive is realized in a simple manner.